From patchwork Wed Apr 1 11:09:05 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiri Olsa X-Patchwork-Id: 1265158 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=kernel.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 48sk3m2ZJ3z9sRf for ; Wed, 1 Apr 2020 22:09:24 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732408AbgDALJX convert rfc822-to-8bit (ORCPT ); Wed, 1 Apr 2020 07:09:23 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:59305 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1732234AbgDALJW (ORCPT ); Wed, 1 Apr 2020 07:09:22 -0400 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-112-0EkIty7hMGeNjH1wd9f-JQ-1; Wed, 01 Apr 2020 07:09:18 -0400 X-MC-Unique: 0EkIty7hMGeNjH1wd9f-JQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2887413FB; Wed, 1 Apr 2020 11:09:16 +0000 (UTC) Received: from krava.redhat.com (unknown [10.40.194.72]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4F5C11001B09; Wed, 1 Apr 2020 11:09:12 +0000 (UTC) From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, Yonghong Song , Martin KaFai Lau , David Miller , John Fastabend , Jesper Dangaard Brouer , Wenbo Zhang , KP Singh , Andrii Nakryiko , bgregg@netflix.com, Al Viro Subject: [PATCH 1/3] bpf: Add support to check if BTF object is nested in another object Date: Wed, 1 Apr 2020 13:09:05 +0200 Message-Id: <20200401110907.2669564-2-jolsa@kernel.org> In-Reply-To: <20200401110907.2669564-1-jolsa@kernel.org> References: <20200401110907.2669564-1-jolsa@kernel.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kernel.org Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Adding btf_struct_address function that takes 2 BTF objects and offset as arguments and checks wether object A is nested in object B on given offset. This function is be used when checking the helper function PTR_TO_BTF_ID arguments. If the argument has an offset value, the btf_struct_address will check if the final address is the expected BTF ID. This way we can access nested BTF objects under PTR_TO_BTF_ID pointer type and pass them to helpers, while they still point to valid kernel BTF objects. Signed-off-by: Jiri Olsa --- include/linux/bpf.h | 3 ++ kernel/bpf/btf.c | 69 +++++++++++++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 18 +++++++++-- 3 files changed, 88 insertions(+), 2 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index fd2b2322412d..d3bad7ee60c6 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1196,6 +1196,9 @@ int btf_struct_access(struct bpf_verifier_log *log, const struct btf_type *t, int off, int size, enum bpf_access_type atype, u32 *next_btf_id); +int btf_struct_address(struct bpf_verifier_log *log, + const struct btf_type *t, + u32 off, u32 exp_id); int btf_resolve_helper_id(struct bpf_verifier_log *log, const struct bpf_func_proto *fn, int); diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index d65c6912bdaf..9aafffa57d8b 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -4002,6 +4002,75 @@ int btf_struct_access(struct bpf_verifier_log *log, return -EINVAL; } +int btf_struct_address(struct bpf_verifier_log *log, + const struct btf_type *t, + u32 off, u32 exp_id) +{ + u32 i, moff, mtrue_end, msize = 0; + const struct btf_member *member; + const struct btf_type *mtype; + const char *tname, *mname; + +again: + tname = __btf_name_by_offset(btf_vmlinux, t->name_off); + if (!btf_type_is_struct(t)) { + bpf_log(log, "Type '%s' is not a struct\n", tname); + return -EINVAL; + } + + if (off > t->size) { + bpf_log(log, "address beyond struct %s at off %u size %u\n", + tname, off, t->size); + return -EACCES; + } + + for_each_member(i, t, member) { + /* offset of the field in bytes */ + moff = btf_member_bit_offset(t, member) / 8; + if (off < moff) + /* won't find anything, field is already too far */ + break; + + /* we found the member */ + if (off == moff && member->type == exp_id) + return 0; + + /* type of the field */ + mtype = btf_type_by_id(btf_vmlinux, member->type); + mname = __btf_name_by_offset(btf_vmlinux, member->name_off); + + mtype = btf_resolve_size(btf_vmlinux, mtype, &msize, + NULL, NULL); + if (IS_ERR(mtype)) { + bpf_log(log, "field %s doesn't have size\n", mname); + return -EFAULT; + } + + mtrue_end = moff + msize; + if (off >= mtrue_end) + /* no overlap with member, keep iterating */ + continue; + + /* the 'off' we're looking for is either equal to start + * of this field or inside of this struct + */ + if (btf_type_is_struct(mtype)) { + /* our field must be inside that union or struct */ + t = mtype; + + /* adjust offset we're looking for */ + off -= moff; + goto again; + } + + bpf_log(log, "struct %s doesn't have struct field at offset %d\n", tname, off); + return -EACCES; + } + + bpf_log(log, "struct %s doesn't have field at offset %d\n", tname, off); + return -EACCES; +} + static int __btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn, int arg) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 04c6630cc18f..6eb88bef4379 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3103,6 +3103,18 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env, return 0; } +static void check_ptr_in_btf(struct bpf_verifier_env *env, + struct bpf_reg_state *reg, + u32 exp_id) +{ + const struct btf_type *t = btf_type_by_id(btf_vmlinux, reg->btf_id); + + if (!btf_struct_address(&env->log, t, reg->off, exp_id)) { + reg->btf_id = exp_id; + reg->off = 0; + } +} + /* check whether memory at (regno + off) is accessible for t = (read | write) * if t==write, value_regno is a register which value is stored into memory * if t==read, value_regno is a register which will receive the value from memory @@ -3696,10 +3708,12 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno, expected_type = PTR_TO_BTF_ID; if (type != expected_type) goto err_type; + if (reg->off) + check_ptr_in_btf(env, reg, meta->btf_id); if (reg->btf_id != meta->btf_id) { - verbose(env, "Helper has type %s got %s in R%d\n", + verbose(env, "Helper has type %s got %s in R%d, off %d\n", kernel_type_name(meta->btf_id), - kernel_type_name(reg->btf_id), regno); + kernel_type_name(reg->btf_id), regno, reg->off); return -EACCES; }